After last Thursday’s unprecedented market meltdown, the early word was that “a massively wrong trade in Procter & Gamble Inc., maybe with a trader entering an order for “billion” instead of “million”” was to blame. But that turns out to have been just a baseless rumor, after all. Widely reported, but baseless.

It seems to have taken an inordinately long amount of time to determine that no billion-share trade had in fact occurred in Procter & Gamble. Every single account I read spoke of investigators sifting through the paper trail that trading generates to verify the existence of such a trade. Nobody explained why this could only be verified by sifting through papers.

Now we’re being told that heavy selling in stock-index futures by one single trader sparked the meltdown. I guess someone arranged for the notion that no single trader is anywhere near big enough to move the largest capital market in the world to be suspended that day? (Let me add, the idea is supposed to be that no one is big enough to move the market by even a slightly significant amount. That one person could move the market by more than 600 points in a matter of minutes is simply unfathomable.)

Regulators examining the causes of the brief stock market free fall last Thursday are looking closely at heavy selling in the market for stock-index futures by a single trader, beginning 10 minutes before stock prices began to plummet.

Gary Gensler, the chairman of the Commodity Futures Trading Commission, said at a Congressional hearing on Tuesday that during that crucial time period, the futures trader, whom he would not identify, accounted for about 9 percent of trading volume in the most actively traded stock-index derivative contract, known as the 500 e-mini futures contract.

All of the trader’s orders were to sell, Mr. Gensler said, while most of the other 250 traders who were active in the same market that day were both buying and selling securities.

As the trader’s orders went through, the futures index on the Chicago Mercantile Exchange began to plummet.

The identity of the trader remained unclear. Terrence A. Duffy, executive chairman of the CME Group, which operates the Chicago exchange, said on Tuesday: “We obviously won’t divulge that market information. We are in contact with the folks that did the trade. There is no question that it is a bona fide hedger” and not someone intending to disrupt the markets.

If I end up eating my words later, so be it, but at this stage I have to say I simply don’t believe it. One, I cannot comprehend how a bona fide hedger could account for “9 percent of trading volume in the most actively traded stock-index derivative contract”. That’s a truly humongous transaction. To be a bona fide hedger, he would have to be protecting the value of an unimaginably large portfolio. Two, given that one trader placed sell orders that accounted for “9 percent of trading volume in the most actively traded stock-index derivative contract”, it’s still hard to conceive how that could move the market so much.

The simple narrative that one single bona fide hedger all by himself accounted for the convulsions the market went through last Thursday simply cannot be the whole truth.

Part of what remains a total mystery at this time is why Procter & Gamble’s shares plunged so much more than any other component of the Dow. It was the 37% drop in Procter & Gamble that had made the billion-million rumor so persuasive, in the first place.